1. Field
The following description relates to a signal processing apparatus and method that enhances a common mode rejection ratio (CMRR) of a signal amplifier by adjusting a common mode signal.
2. Description of Related Art
A differential amplifier may refer to a circuit that amplifies a voltage difference between two input signals. During operation of the differential amplifier, a single-ended operation may apply an input signal to a single input terminal only and ground a remainder of input terminals. A double-ended or differential-mode operation may apply two input signals having opposite polarities to the differential amplifier. Further, a common mode operation may apply an identical input signal to two input signals.
In the common mode operation, an output signal of an ideal differential amplifier may be zero. In actuality, however, an output signal may fail to be zero due to various factors. For example, an infinitesimal signal may be output when an identical signal is input as the two input signals. A large signal may be output when an opposite pole signal is inputted. A common mode rejection ratio (CMRR) may refer to a ratio of a differential mode gain to a common mode gain. The CMRR may be used as a standard indicating a performance of the differential amplifier. For example, the differential amplifier has a better performance the higher the CMRR.